program Task3;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var
  n, a, i:integer;
begin                               
  readln(n);
  a:=0;
  if (n mod 2=0) then
  begin
    for i:= 1 to n div 2 do
    begin
      a:=a+(2*i);
    end;
    writeln(a);
  end;
  if (n mod 2=1) then
  begin
    for i:= 1 to n div 2 do
    begin
      a:=a+(2*i+1);
    end;
    writeln(a);
  end;
  readln;
end.
